Hammertoe Implant with Asymmetrical Head

ABSTRACT

An intramedullary fixation device used in bone fixation and stabilization on a patient includes a longitudinally extending rigid body and a distal head disposed at a distal end of the body. The distal head includes a central core portion and a plurality of extending distal wings radially projecting from the central core portion, wherein the radially projecting distal wings are spaced asymmetrically about the central core portion. A proximal head at a proximal end of the body and sized for insertion into an intramedullary canal of a phalanx of the patient. The proximal head includes a central core portion and a plurality of proximal wings extending radially outwardly from the central core portion.

PRIORITY

The present disclosure claims priority to and the benefit of the filingdate of U.S. Provisional Application 61/780,316, filed Mar. 13, 2013,incorporated herein by reference.

BACKGROUND

Hammertoe deformities occur when the metatarsophalangeal joint betweenphalanges in a toe are cocked upward and the proximal interphalangealjoint bends downward. This deformity can become quite painful and canlimit the ability of a person with hammertoe to walk and perform otherdaily activities. Hammertoe may be caused by any number of factors,including heredity, the long-term use of poorly fitting shoes, having along second toe, hallux valgus pressing against the second toe,connective tissue disorders and trauma.

While some minor cases may be treated with non-surgical remedies,surgeries are often necessary to provide real correction and painrelief. Some surgical methods include stabilizing the toes using asmooth K-wire placed in an antegrade manner through the middle anddistal phalanges while joint extension and distraction are maintained.The K-wire may then be placed in retrograde fashion into the proximalphalanx while joint extension and distraction are maintained. Fixationlasts for 4-6 weeks after surgery. During that time, the pins are cappedso that the sharp ends do not catch on objects, such as bed sheets. Evenwith this form of fixation, non-unions, K-wire migration, and loss offixation can be quite common. Further, the external K-wires may lead topin tract infections or movement of bone along the smooth wire,including rotation of the distal aspect of the toe. These types ofchallenges make alternative fixation methods desirable.

The system and methods disclosed herein overcome one or more of thedeficiencies of the prior art.

SUMMARY

In one exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilizationon a patient. The device includes a longitudinally extending rigid bodyand a distal head disposed at a distal end of the body. The distal headincludes a central core portion and a plurality of extending distalwings radially projecting from the central core portion, wherein theradially projecting distal wings are spaced asymmetrically about thecentral core portion. A proximal head is disposed at a proximal end ofthe body and is sized for insertion into an intramedullary canal of aphalanx of the patient. The proximal head includes a central coreportion and a plurality of proximal wings extending radially outwardlyfrom the central core portion.

In an exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilizationon a patient. The device includes a longitudinally extending rigid bodyhaving a rigidity sufficient to withstand bending loading applied by thephalanges. The rigid body has a longitudinal axis extending through at aleast a portion of the body. The device also includes a distal headdisposed at a distal end of the body and sized for insertion into anintramedullary canal of a phalanx of the patient. The distal head has acentral core portion and a plurality of extending distal wings radiallyprojecting from the central core portion. The radially projecting distalwings are spaced asymmetrically or symmetrically about the central coreportion. The device also includes a proximal head at a proximal end ofthe body that is sized for insertion into an intramedullary canal of aphalanx of the patient, the proximal head having central core portionand a plurality of proximal wings extending radially outwardly from thecentral core portion.

In an aspect, the distal head has a first maximum width and the proximalhead has a second maximum width, the first maximum width being greaterthan the second maximum width. In an aspect, the distal head has a firstlongitudinal wing length and the proximal head has a second longitudinalwing length, the first longitudinal wing length being less than thesecond longitudinal wing length. In an aspect, the asymmetricallyspaced, radially projecting distal wings form a T-shape. In an aspect,the device comprises a planar surface extending entirely across thetransverse width of the distal head portion. In an aspect, at least onethe proximal wings or the distal wings has a profile that iswedge-shaped. In an aspect, each proximal wing comprises an outersurface portion forming an outer perimeter surface, the outer surfaceportion comprising an outer perimeter surface portion and a curvedleading surface portion, the curved leading surface portion curving fromthe outer perimeter surface portion and smoothly intersecting at thecentral core portion of the proximal head, each proximal wing alsocomprising a distally facing trailing surface portion substantiallyperpendicular to the longitudinal axis of the rigid body. In an aspect,each distal wing comprising an outer surface portion having an outerperimeter surface portion and a curved leading surface portion, thecurved leading surface portion curving from the outer perimeter surfaceportion and smoothly intersecting at the central core portion of thedistal head, each wing of the distal head also comprising a proximallyfacing trailing surface portion substantially perpendicular to thelongitudinal axis of the rigid body.

In another exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilizationon a patient. The device includes a longitudinally extending rigid bodyhaving a rigidity sufficient to withstand bending loading applied by thephalanges, the rigid body having a longitudinal axis extending throughat a least a portion of the body. The device also includes a distal headdisposed at a distal end of the body and sized for insertion into anintramedullary canal of a phalanx of the patient. The distal head has acentral core portion and at least three radially extending distal wingsradially projecting from the central core portion. Two of the wings forma planar surface extending entirely across the width of the distal head.The device also includes a proximal head at a proximal end of the bodyand sized for insertion into an intramedullary canal of a phalanx of thepatient. The proximal head has a central core portion and a plurality ofproximal wings extending radially outwardly from the central coreportion.

In an aspect, the radially projecting distal wings are spacedasymmetrically about the central core portion. In an aspect, the distalhead has a first maximum width and the proximal head has a secondmaximum width, the first maximum width being greater than the secondmaximum width. In an aspect, the distal head has a first longitudinalwing length and the proximal head has a second longitudinal wing length,the first longitudinal wing length being less than the secondlongitudinal wing length. In an aspect, the asymmetrically spaced,radially projecting distal wings form a T-shape. In an aspect, thedevice comprises a planar surface extending entirely across thetransverse width of the distal head portion. In an aspect, at least onethe proximal wings or the distal wings is wedge-shaped. In an aspect,each proximal wing comprises an outer surface portion forming an outerperimeter surface, the outer surface portion comprising an outerperimeter surface portion and a curved leading surface portion, thecurved leading surface portion curving from the outer perimeter surfaceportion and smoothly intersecting at the central core portion of theproximal head, each proximal wing also comprising a distally facingtrailing surface portion substantially perpendicular to the longitudinalaxis of the rigid body. In an aspect, each distal wing comprising anouter surface portion having an outer perimeter surface portion and acurved leading surface portion, the curved leading surface portioncurving from the outer perimeter surface portion and smoothlyintersecting at the central core portion of the distal head, each wingof the distal head also comprising a proximally facing trailing surfaceportion substantially perpendicular to the longitudinal axis of therigid body.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory innature and are intended to provide an understanding of the presentdisclosure without limiting the scope of the present disclosure. In thatregard, additional aspects, features, and advantages of the presentdisclosure will be apparent to one skilled in the art from the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate embodiments of the devices andmethods disclosed herein and together with the description, serve toexplain the principles of the present disclosure.

FIG. 1 is an illustration of an exemplary intramedullary fixation devicedisposed between and within adjacent phalanges of a toe of a patient inaccordance with one aspect of the present disclosure.

FIGS. 1A-1D are illustrations of exemplary intramedullary fixationdevices disposed between and within adjacent phalanges of a toe of apatient in accordance with different aspects of the present disclosure.

FIGS. 2-6 are illustrations of another exemplary intramedullary fixationdevice in accordance with one aspect of the present disclosure.

FIG. 7 is an illustration of another exemplary intramedullary fixationdevice in accordance with one aspect of the present disclosure.

FIG. 8 is illustrations of another exemplary intramedullary fixationdevice in accordance with one aspect of the present disclosure.

FIGS. 9-13 are illustrations of another exemplary intramedullaryfixation device in accordance with one aspect of the present disclosure.

FIGS. 14-18 are illustrations of another exemplary intramedullaryfixation device in accordance with one aspect of the present disclosure.

FIG. 19 is an illustration of an exemplary intramedullary fixationdevice disposed between and within adjacent phalanges of a hand of apatient in accordance with one aspect of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the disclosure is intended. Any alterations and furthermodifications to the described devices, instruments, methods, and anyfurther application of the principles of the present disclosure arefully contemplated as would normally occur to one skilled in the art towhich the disclosure relates. In particular, it is fully contemplatedthat the features, components, and/or steps described with respect toone embodiment may be combined with the features, components, and/orsteps described with respect to other embodiments of the presentdisclosure. For simplicity, in some instances the same reference numbersare used throughout the drawings to refer to the same or like parts.

The present disclosure relates to intramedullary systems, methods, anddevice used for bone fixation and stabilization of toes and fingersacross fusion or fracture sites, and treat deformities, including forexample, hammertoe deformities. The intramedullary fixation deviceincludes unique arrow designs on both its proximal and distal ends, andin some embodiments, with the arrow designs varying in size and shape.It is arranged to be completely intramedullary when implanted with noparts of the device exposed outside the skin. Further, it is arranged toresist the rotational and pull-out forces affecting all digits or toesand fingers. Its particular design shape may help it maintain theinitial compression applied at insertion.

FIG. 1 shows an exemplary toe 10 having an intermediate phalanx 12 and aproximal phalanx 14. In this example, the toe 10 has been surgicallytreated to correct a deformity such as hammertoe as discussed above.Accordingly, the toe includes an implanted intramedullary fixationdevice 100 disposed therein in accordance with an exemplary aspect ofthe present disclosure. In this example, the device 100 extends betweenand is implanted within the intermediate and proximal phalanges 12, 14.It is described in detail below.

FIG. 1A shows the exemplary device 100 in greater detail configured anddisposed to anchor in the cortex or cancellous bone of the proximalphalanx and the intermediate phalanx. FIG. 1B shows an exemplary device110 configured and disposed to anchor in the subchondral bone of theproximal phalanx and cancellous bone or cortex in the intermediatephalanx.

FIG. 1C shows an exemplary device 120 configured and disposed to anchorin the subchondral bone of the proximal phalanx, to entirely passthrough the intermediate phalanx, and to anchor in the distal phalanx.

FIG. 1D shows an exemplary device 130 configured and disposed to anchorin the middle phalanx and the distal phalanx. The devices described ingreater detail may form or be used to form any of the devices 100, 110,120, and 130 shown in FIGS. 1 and 1A-1D, with dimensional changes beinga difference between devices.

FIGS. 2-6 show another exemplary embodiment of a device, referencedherein as a device 200 that may be implanted in the manner shown inFIGS. 1 and 1A to 1D. The device 200 is designed with athree-dimensionally configured arrow at each end and includes a distalhead 202, a proximal head 204, and a body 206 extending between thedistal and proximal heads 202, 204 and having a longitudinal axis 207.Features consistent with those described above will not be repeated herefor the sake of simplicity, but it is understood that the relevantdescription of features relative to other embodiments described hereinalso apply to the device 200.

The distal head 202 includes a central core portion 208 and a pluralityof radially extending wings 210. The core portion 208 extends along thelongitudinal axis 207 of the body 206 and includes the distal end 212.In this example, the distal end 212 is rounded or blunt end to providesmooth insertion into the medullary canal. In addition, because of itsrounded shape, when implanted in techniques using bored or reamed holes,the surgeon can feel tactilely when the implant is inserted to the depthof the bored or reamed hole because the rounded end resists furtherinsertion at low insertion forces. However, the surgeon may still insertthe device into the intramedullary canal beyond the end of the bored orreamed area by applying additional force. In this embodiment, the distalend 212 is formed of a convexly shaped leading nub 214 extending fromthe surfaces leading to the wings 210.

The plurality of wings 210 extend radially from the core portion 208 anddefine the outer shape of the distal head 202. In the embodiment shown,the head 202, as measured from wing to wing, has a diameter sized to fitwithin an intramedullary canal of a phalanx and more particularly,within a medullary canal of a middle phalanx.

The wings themselves include an outer surface portion 216, a trailingsurface portion 222, and lateral sides 224. In the exemplary embodimentshown, the outer surface portion 216 of the wings 210 includes acylindrical surface portion 218 and a curved leading surface portion220. The outer perimeter surface portion 218 extends in the longitudinaldirection and then intersects with the curved leading surface portion220. In this example, the outer perimeter surface portion 218 of theplurality of wings 210 together also defines an outer diameter or outerwidth W1 (FIG. 3) of the distal head 202. In some embodiments, the headhas a width sized within the range of about 2.0 mm to 15 mm. In someembodiments, the width is in a range of about 2.0 mm to 4.5 mm. In oneembodiment, the width W1 is sized within the range of about 3.0 mm to4.0 mm. In one embodiment, the width W1 is sized within the range ofabout 3.5 mm. In some embodiments, the height of individual wings asmeasured radially from the axis may vary between different orientations.For example, wings extending in a lateral direction may have a heightdifferent than adjacent wings extending in a cross-lateral direction. Insome embodiments, the outer perimeter surface portion 218 of the wings210 has a curved outer surface that lies along the boundary of acylindrical shape at the maximum diameter or width W1, as represented bythe dashed lines in FIG. 3. Some embodiments are sized to accommodate aparticular bone quality and intramedullary canal diameter. For example,for softer bone quality or for larger canals, the diameter of the distalhead may be selected to be within a range of 2.5 mm to 5.0 mm.

Extending from the outer perimeter surface portion 218, the wings 210include the curved leading surface portion 220. The curved leadingsurface portion 220 faces at least partially in the direction of thedistal end 212, and curves from the outer surface portion 216 toward andsmoothly intersects with the core portion 208. In some embodiments, thecurved leading surface portion 220 has a radius within a range of about1 mm to 10 mm, in some embodiments, it has a radius within a range ofabout 1 mm to 4 mm, and in some embodiments has a radius within a rangeof about 1.5 mm to 2.5 mm. In one embodiment, the radius is 2 mm.

The trailing surface portion 222 is a surface extending radially inwardfrom the outer surface portion 216 toward the longitudinal axis of thedevice 200 and intersects with the core portion 208. In the embodimentshown, the trailing surface portion 222 has a surface that liessubstantially normal to the longitudinal axis 207, although in otherembodiments, it may be angled obliquely relative to the longitudinalaxis. A rounded, distally projecting edge 228 connects the trailingsurface portion 222 to the outer perimeter surface portion 218 of theouter surface portion 216.

In the embodiment shown, each wing 210 includes two lateral sides 224.In the example shown, the lateral sides extend from the outer surfaceportion 216 to the core portion 208. Depending on the embodiment, theselateral sides 224 may be formed in parallel planes or may bewedge-shaped. The thickness of the wing 210 is defined by the distancebetween the lateral sides 224 and the pull-out resistance is determinedby the thickness of the wing 210 at the trailing surface portion. A wing210 having lateral sides 224 in parallel planes will have uniformthickness and may be easier to implant while still providing rotationalstability.

In other embodiments however, these lateral sides 224 may be formed ofnonparallel planes and may form a wedge-shape. For example, oneembodiment includes a wing 10 having a leading portion having athickness about 0.38 mm at the leading end and a thickness of about 0.52mm at the trailing end. Other angles are dimensions are alsocontemplated. Accordingly, the wings are thinner toward the leading endthan the trailing end. Embodiments with wedge-shaped wings may requiremore force to implant. However, they may also provide closer contactbetween the bone and the wing 210 because the wing may become graduallythicker from the leading edge to the trailing edge. In addition,increasing thickness of the wing toward the trailing edge maximizes theresistance to pull-out because the wing at the trailing surface portionis at its thickest location.

In some embodiments, the lateral sides 224 are nonplanar and have acurved surface that promotes interference with bone tissue to resistmigration and rotation. Some embodiments include wings that vary by wingthickness. For example, some embodiments include two wings having afirst thickness and two additional wings having a second thicknessgreater than the first thickness. The core portion 208 smoothly connectsand spans between adjacent wings with a cylindrical surface 232 thatextends the length of the wings 210.

Because the distal end 212 has a smooth bullet-nose shape, thelikelihood of the distal end catching on the cortex and preventing theimplant from being advanced smoothly may be diminished. Duringinsertion, the wings 210 act as sled runners to help the device 200slide easily down a reamed pilot hole. In addition, the smooth andcurved leading surface portion 220 on the wings 210 may enable theimplant to be self-centering during the insertion process.

While the distal head 202 is shown having four wings 210 forming a plusor cruciate configuration, other embodiments include a different numberof wings. One embodiment includes three wings, while another embodimentincludes two wings. Yet other embodiments include more than four wings.The number of wings may affect the pull-out resistance of the device200. For example, a balance between the number of wings and theirrelative size may permit the device to be designed to achieve a desiredpull-out resistance. Reducing the diameter of the wings may permit thedevice 200 to be implanted within smaller diameter intramedullary canalswhile still providing suitable resistance to pull-out. Some embodimentshave the wings of the proximal head rotatably offset from the wings ofthe distal head. For example, while the wings on the distal head may bedisposed at 3, 6, 9, and 12 o'clock, the wings on the proximal head maybe disposed at 2, 5, 8, and 11 o'clock. In some embodiments, the wingsare offset by 45 degrees.

Because of the central core portion 208 design, the pilot holepreparation may be done with a rotary motion, such as a power or manualreamer or drill, thereby possibly reducing the need for the step ofbroaching the pilot hole to form a rectangular cavity.

Some embodiments include a head length that is minimized in order topermit as much bone growth behind the trailing surface portion possibleto contribute to resistance to pull-out. In one embodiment, the lengthof the distal head is within the range of about 2.0 mm to 3.0 mm. Othersizes are also contemplated.

The blade orientation for the distal head 202 provides not onlyresistance to rotation and pull-out but also may ease pulling the middlephalanx over the distal head 202 as the device protrudes from theproximal phalanx

The proximal head 204 includes a central core portion 240 and aplurality of radially extending wings 242. Many features of the proximalhead 204 are similar to that of the distal head 202 and not all thefeatures are re-described here, recognizing that one of ordinary skillwould understand that features and alternatives described relative tothe distal head 202 have equal applicability to the proximal head 204.Like the core portion 208 of the distal head 202, the central coreportion 240 extends along the longitudinal axis 207 of the body 206. Thecore portion 240 includes a proximal end 244. In this example, the coreportion 240 and the proximal end 244 differs in shape as describedbelow, while still maintaining a rounded or blunt end to provide smoothinsertion into the medullary canal. In this embodiment, the core portionproximal end 244 includes a conical surface portion 256 that connectsthe leading surface portion 250 and includes a convexly shaped leadingnub 245 extending from the surfaces leading to the wings 242.

The plurality of wings 242 extend radially from the core portion 240 anddefine the outer shape of the proximal head 204. In the embodimentshown, the head 202, as measured from wing to wing, has a diameter sizedto fit within an intramedullary canal of a phalanx and moreparticularly, within a canal of a proximal phalanx.

The wings 242 themselves include an outer surface portion 246, atrailing surface portion 252, and lateral sides 254. In the exemplaryembodiment shown, the outer surface portion 246 of the wings 242includes an outer perimeter surface portion 248 and a curved leadingsurface portion 250. The outer perimeter surface portion 248 extends inthe longitudinal direction and then intersects with the curved leadingsurface portion 250. In this example, the outer perimeter surfaceportion 248 of the plurality of wings 242 together also defines an outerdiameter or outer width W2 (FIG. 6) of the distal head 202. In someembodiments, the proximal head 204 has a width sized within the range ofabout 1.0 mm to 3.5 mm. In one embodiment, the width W2 is sized withinthe range of about 2.0 mm to 3.0 mm. In one embodiment, the width W2 issized within the range of about 2.5 mm. In some embodiments, the outerperimeter surface portion 248 of the wings 242 has a curved outersurface that lies along the boundary of a cylindrical shape at themaximum diameter or width W2, as represented by the dashed lines in FIG.6.

Extending from the outer perimeter surface portion 248, the wings 242include the curved leading surface portion 250. The curved leadingsurface portion 250 curves from the outer surface portion 216 toward andsmoothly intersecting with the conical surface portion 256 of the coreportion 208. In some embodiments, the curved leading surface portion 250has a radius sized in the ranges as described with reference to thecurved leading surface portion 220. In one embodiment, the coveredleading surface portions 220, 250 have the same radius.

The trailing surface portion 252 extends radially inward from the outersurface portion 246 toward the longitudinal axis of the device 200 andintersects with the core portion 240. A rounded edge 258 connects thetrailing surface portion 252 to the outer perimeter surface portion 248of the outer surface portion 246.

Each wing 242 includes two lateral sides 254. In one embodiment, thethickness of the wings 242 is measured between the lateral sides 254 andis in the range of 0.020 mm and 0.060 mm. In one embodiment, the wingsare wedge shaped and taper from a thickness of 0.37 mm at its leadingend to 0.053 at its trailing end.

As indicated above, the overall length of the proximal head 204 isgreater than that of the distal head 202. However, the length can beshortened to enhance pull-out resistance. For example, the resistance topull-out may increase as the distance from the trailing surface portionof the distal or proximal head to the resection increases. For thedistal head 202 that is implanted in the middle phalanx, a shorter headmay offer resistance to rotation and still increase the distance fromthe trailing surface portion of the implant wings to the resection sitewhen implanted to the same depth. Because the trailing surface portionof the wing on the shorter head is farther from the fracture site, aradiograph would give the appearance of the device being more deeplyimplanted in the middle phalanx. As such the distal head 202 with itslarger diameter is intended for implantation in the medial phalanx andthe proximal head 204 with its smaller diameter is intended forimplantation in the proximal phalanx.

The body 206 is a rigid shaft extending between and connecting thedistal head 202 and the proximal head 204. In the embodiment shown, thebody 206 is cylindrically shaped and has a substantially smooth exteriorsurface. In one embodiment, the body 206 has a diameter or across-sectional thickness within a range of about 1.2 mm to 2.0 mm. Inone embodiment, the body 206 has a diameter or a cross-sectionalthickness of about 1.6 mm. Other sizes, larger and smaller arecontemplated. The body 206 includes a necked-down region adjacent theproximal and distal head as the body merges with the central coreportion.

In some embodiments, the proximal and distal heads form about a 30% orless of the overall length of the device. In one example, the distalhead has a length of about 2.5 mm, the proximal head has a length ofabout 3.0 mm, and the body has a length about 13.5 mm or greater.

Some embodiments of the body 206 include a plantar grade bend. Differentembodiments include a bend that may be selected in the range of about5-25 degrees. In some examples, the bend is selected to be about a 15degree bend, while yet other embodiments the bend is selected to beabout a 10 degree bend, an in another, about a 5 degree bend.

In the embodiment shown, the body 206 has a substantially constantdiameter. However some embodiments have body diameters that vary alongthe length of the body 206 to correspond to forces and to increase thearea of the arrowhead tip resisting pull-out and rotational forces. Twosuch embodiments are described below relative to FIGS. 7 and 8.

FIG. 7 shows another embodiment of a device referenced herein by thenumeral 300. The device 300 includes a distal head 302, a proximal head304, and a body 306. The distal and proximal heads 302, 304 includefeatures similar to those described above, and the descriptions apply tothis embodiment, recognizing that the size ratio of the different headsmay differ on the device 300. Here, the proximal head 304 includes acore portion 308 and wings 310. The body 306 in this embodiment includesa tapered shaft region 312 that extends along a substantial portion ofthe body 306.

In this embodiment, the size ratio of tapered shaft region 312 to theadjacent core portion 308 of the head may be selected to be minimizedThis may permit the body 306 to be deeply embedded within the phalanxwith a minimal amount of tissue disruption. Some embodiments have lessthan a 1:1.5 tapered shaft region to core portion size ratio, whileother embodiments have a 1:1 size ratio. Other sizes and ratios arecontemplated. The reduced diameter of the tapered shaft region 308 mayextend less than half the distance of the body 306 so that the thickerregion of the body 306 may be disposed at the fusion region when thedevice 200 is implanted. In the exemplary embodiment shown, the taperedshaft region 312 extends for a length of more than about 15% of thelength of the entire body. In one embodiment, the tapered shaft region312 extends from the proximal head a distance between about 15% and 45%of the length of the body 306. In some examples, the tapered shaftregion 312 extends a distance within a range of about 20% and 30% of thelength of the body 306. This may provide a suitable region for boneingrowth behind the proximal head 304, while still having the thickerportion of the body at the resection site. While referred to as atapered shaft region 312, the narrow region of the shaft may also becylindrical, and may be referred to as a narrow region.

This also may permit the proximal head 304 to be embedded in thesubchondral bone of the proximal phalanx. Reducing the ratio of the coreportion 308 to the body 306 may increase the resistance to rotation andpull-out. In one embodiment, the body diameter or width is set at adiameter of 10 mm so that an additional 0.25 mm per wing (0.5 mm total)is available to resist rotational forces. The increased area resistingpull-out is also 0.25 mm per wing multiplied by the width of the wing310 at the trailing surface portion, multiplied by the number of wings310. In this embodiment, a reamer width would be reduced to the width ofthe body 306 at the narrowest point.

In the example shown, the thickness or cross-sectional width of the body306 that aligns with the resection site and into the distal tip of theimplant would remain at the thickest portion of the body 306, which inone embodiment, is 1.6 mm.

FIG. 8 shows another embodiment of a device, reference herein by thenumeral 400. The device 400 includes a distal head 402, a proximal head404, and a body 406. The distal and proximal heads 402, 404 includefeatures similar to those described above, and the descriptions apply tothis embodiment, recognizing that the size ratio of the different headsmay differ on the device 400. In this embodiment, the body 406 includesa central region 410 of increased thickness. Accordingly, the body 406includes narrower regions 412 at the distal and proximal ends, and thesenarrow further at necks 414 to form the respective distal and proximalheads 402, 404.

Here, the central region 410 may provide greater strength and a tighterfit at the site of the resection. In one embodiment, the width ordiameter of the body 106 in the central region 410 is within a range ofabout 1.8 mm-2.2 mm to enhance the fixation at the resection site and tostabilize the device by helping to reduce play of the device 200. Thismay also increase the strength of an already strong implant at the pointof greatest potential stresses. In such an embodiment, the reamerdiameter may remain at a size to accommodate the narrower regions 412.For example, the narrow regions 412 may have a diameter of about 1.6 mm,and therefore, in some examples, the reamer diameter would also be 1.6mm. In one embodiment, the central region 410 may extend about 40-70% ofthe length of the body. In other embodiments, the central region extendsabout 40-60% of the length of the body.

Some embodiments of the bodies disclosed herein include a coating ortissue growth material. For example, some embodiments include anaggressive porous material or coating that is “sticky” to tissue. Someexamples include a bone-growth promoting substance, such as, forexample, a hydroxyapatite coating formed of calcium phosphate,tricalcium phosphate (TCP), and/or calcium carbonate. Alternatively,osteoinductive coatings, such as proteins from transforming growthfactor (TGF) beta superfamily, or bone-morphogenic proteins, such asBMP2 or BMP7, may be used. These coatings may increase adhesion tocancellous bone, increasing resistance to pull-out and rotationalforces. They also may accelerate bony ingrowth and accelerateconsolidation of the bone. The coating may be applied along the entirebody of the device, or may be applied only along a specific region, suchas a region, that is half of the body adjacent the distal head, forexample. FIG. 5 shows one example of a coating region, identified by thebox labeled CR. The coating may be arranged in other ways also.

Although shown as cylindrical, any of the bodies disclosed herein mayhave a cross-section of any suitable shape, and may include, forexample, a shaft shape that is triangular shaped, square shaped or onewith edges rather than cylindrical. These types of body cross-sectionscan provide additional resistance to rotational forces. In anotherexample, edges emerging from the body can serve to provide additionalfixation.

In some embodiments, the proximal head of the devices is sized andconfigured to be embedded in the subchondral bone at the base of theproximal phalanx. The rounded blunt tip may require greater force thanthe sharper, pointier arrow of the other embodiments to progress fartherinto the subchondral bone than the prepared hole provides. Accordingly,the blunt bullet nose may prevent the implant from advancing past theend of the reamed pilot hole.

In one embodiment, the length of the proximal head is about 2.0 mm inthe longitudinal direction. This length permits the addition of one ortwo additional wings that may increase both the level of the resistanceto rotation and pull-out without increasing the length of the arrowhead.Increasing the length could adversely affect the pull-out resistance invivo, for example, if the longer arrowhead were to not be completelyembedded in subchondral bone. In this example, the wings are formed sothat the head is substantially symmetrical.

FIGS. 9-13 show an additional embodiment of a device, referenced hereinby the numeral 500, including a distal head 502, a proximal head 504,and a body 506. The distal and proximal heads 502, 504 include featuressimilar to those described above, and the descriptions apply to thisembodiment, recognizing that the size ratio of the different heads maydiffer on the device 500. In this embodiment, the distal and proximalhead each include three wings radially extending from a central core. Ascan be seen, and consistent with the description above, the distal headhas a greater width and a smaller length than the proximal head. Here,as can be seen in the end views shown in FIGS. 10 and 11, the wings ofthe distal head and the proximal head are rotationally offset. Sincethere are three wings, they are rotationally offset by 60 degrees.

FIGS. 14-18 show an additional embodiment of a device, referenced hereinby the numeral 600, including a distal head 602, a proximal head 604,and a body 606. The distal and proximal heads 602, 604 include featuressimilar to those described above, and the descriptions apply to thisembodiment, recognizing that the size ratio of the different heads maydiffer on the device 600.

In this embodiment however, the proximal head 604 includes four wingsand may be similar to those discussed above, the distal head 602includes a non-symmetric head providing specific advantages.

In this embodiment, the distal head 602 includes three wings 610 spacedabout an axis of the device 600. For reference, the wings are identifiedas 610 a, 610 b, and 610 c. The wings 610 a and 610 c are spaced 90degrees apart from adjacent wing 610 b, but, the wings 610 a and 610 care adjacent and spaced 180 degrees apart, forming an asymmetric distalhead 602. Accordingly, a plantar wing is not present. Therefore, thesewings 610 a and 610 c form a planar surface and the wing 610 b, alsoreferred to as the dorsal wing, extend perpendicular away from theplanar surface.

As such, the distal head 602 is configured to provide rotationalstability with the three present wings, but also may be easier to insertinto a phalanx during surgery. For example, by orienting the device andinserting the device in the proper arrangement, the distance the middlephalanx would need to be extended to place the distal tip of the implantnear the prepared pilot hole may be less than with a plantar wing inplace.

In this embodiment, the distal head 602 forms a T-shaped configurationwith the planar surface extending from one side to the other. The planarsurface is parallel to but offset from the central longitudinal axis.Further, as can be seen in FIG. 16, a plane along the planar surfaceintersects the body 606 of the device 600. Another embodiment may orientthe 3 wings at different angles (10 o'clock, 12 o'clock and 2 o'clock).

One embodiment employs a sideways X-wing cross-section (having acute andoblique angles between adjacent wings) to provide the balance betweenease of use and stability.

The devices may be implanted using any of a number of surgicalinstruments or tools, including for example, a reamer, a broach, and aninsertion forceps. These instruments are described in detail in priorU.S. patent application Ser. No. 13/084,048 to Roman, filed Apr. 11,2011, and incorporated herein by reference.

Furthermore, the devices disclosed herein may be provided as a kit incombination with a plurality of devices of different sizes or theinstruments themselves. One exemplary kit includes a device as describedabove, with the reamer, the broach, and the insertion forceps. Otherkits are described in prior U.S. patent application Ser. No. 13/084,048to Roman, filed Apr. 11, 2011, and incorporated herein by reference.

The devices herein may be used in exemplary surgical methods forimplanting the device for the treatment or correction of bonedeformities. When implanted, the arrowhead configuration of both thedistal and proximal heads captures bone on both sides of the fusion orfracture site, and may provide internal stability. This is accomplishedby pressing and locking the distal and proximal heads into thesurrounding bone. The body of the device extends from each head(proximal and distal) and is the portion of the implant that crosses orspans the fusion or fracture site.

It should be noted that the exemplary devices described herein may beused for treatments such as hammertoe, and in some examples, may be usedto treat conditions in the fingers of a hand, or alternatively may beused to treat bone fractures. FIG. 19 is one example, which could be anyof the devices disclosed herein implanted within phalanges of the hand.In addition, removal of the device may be relatively easier than prior,conventional devices. For example, to remove the device, the cylindricalmain body may be first cut, and then a cannulated drill may be fit overthe cylindrical main body and drilled over to remove bony on-growth fromthe cylindrical body so that the arrowhead tip can be removed withouttearing the bone. This may prevent the health care provider from havingto cut the cortical bone in order to remove the implant. Accordingly,the cylindrical shape of the main body may help reduce a chance ofcompromising cortical bone during revision surgeries. Uses of the devicemay include but are not limited to hand surgery, orthopedic surgery,plastic surgery, and podiatric surgery. In addition, the implant may beinserted in a variety of angles that differ from its intended positionin medullary bone. In some examples, the implant may also be placedthrough cortical bone and tendon of the hand or foot.

In some examples, the device is machined from a single piece of 316Lstainless steel, making it a weld-less, single monolith structure. Inother embodiment, it may be formed of two structures welded or brazedtogether. Various lengths may be provided to meet patient sizingrestrictions. The overall lengths of the device may be in the range of10 mm to 70 mm, while some lengths may be within the range of 10 mm to40 mm, while yet additional lengths are within the range of 15 mm to 25mm When the device is formed of a single piece of metal, potentialstress-risers occurring from welds or adhesives are eliminated and thereis no need to assemble intra-operatively. Further, the material and sizeare selected so that the device has bending and fatigue characteristicsable to endure the forces exerted on the lesser toes.

In some examples, the arrowheads may be reconfigured at differentpositions to one another and may obtain the same stability to thearthrodesis/fracture site. For example, some embodiments have a proximalarrow vertical to the shaft or a distal arrow horizontal to the shaft.The same can be said for different angle increments to each arrow.

Persons of ordinary skill in the art will appreciate that theembodiments encompassed by the present disclosure are not limited to theparticular exemplary embodiments described above. In that regard,although illustrative embodiments have been shown and described, a widerange of modification, change, and substitution is contemplated in theforegoing disclosure. It is understood that such variations may be madeto the foregoing without departing from the scope of the presentdisclosure. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the presentdisclosure.

We claim:
 1. An intramedullary fixation device used in bone fixation andstabilization on a patient, comprising: a longitudinally extending rigidbody having a rigidity sufficient to withstand bending loading appliedby the phalanges, the rigid body having a longitudinal axis extendingthrough at a least a portion of the body; a distal head disposed at adistal end of the body and sized for insertion into an intramedullarycanal of a phalanx of the patient, the distal head having a central coreportion and a plurality of extending distal wings radially projectingfrom the central core portion, wherein the radially projecting distalwings are spaced asymmetrically about the central core portion; and aproximal head at a proximal end of the body and sized for insertion intoan intramedullary canal of a phalanx of the patient, the proximal headhaving central core portion and a plurality of proximal wings extendingradially outwardly from the central core portion.
 2. The intramedullaryfixation device of claim 1, wherein the distal head has a first maximumwidth and the proximal head has a second maximum width, the firstmaximum width being greater than the second maximum width.
 3. Theintramedullary fixation device of claim 1, wherein the distal head has afirst longitudinal wing length and the proximal head has a secondlongitudinal wing length, the first longitudinal wing length being lessthan the second longitudinal wing length.
 4. The intramedullary fixationdevice of claim 1, wherein the asymmetrically spaced, radiallyprojecting distal wings form a T-shape.
 5. The intramedullary fixationdevice of claim 1, further comprising a planar surface extendingentirely across the transverse width of the distal head portion.
 6. Theintramedullary fixation device of claim 1, wherein at least one theproximal wings or the distal wings is wedge-shaped.
 7. Theintramedullary fixation device of claim 1, wherein each proximal wingcomprises an outer surface portion forming an outer perimeter surface,the outer surface portion comprising an outer perimeter surface portionand a curved leading surface portion, the curved leading surface portioncurving from the outer perimeter surface portion and smoothlyintersecting at the central core portion of the proximal head, eachproximal wing also comprising a distally facing trailing surface portionsubstantially perpendicular to the longitudinal axis of the rigid body.8. The intramedullary fixation device of claim 7, wherein each distalwing comprising an outer surface portion having an outer perimetersurface portion and a curved leading surface portion, the curved leadingsurface portion curving from the outer perimeter surface portion andsmoothly intersecting at the central core portion of the distal head,each wing of the distal head also comprising a proximally facingtrailing surface portion substantially perpendicular to the longitudinalaxis of the rigid body.
 9. An intramedullary fixation device used inbone fixation and stabilization on a patient, comprising: alongitudinally extending rigid body having a rigidity sufficient towithstand bending loading applied by the phalanges, the rigid bodyhaving a longitudinal axis extending through at a least a portion of thebody; a distal head disposed at a distal end of the body and sized forinsertion into an intramedullary canal of a phalanx of the patient, thedistal head having a central core portion and at least three radiallyextending distal wings radially projecting from the central coreportion, two of the wings forming a planar surface extending entirelyacross the width of the distal head; and a proximal head at a proximalend of the body and sized for insertion into an intramedullary canal ofa phalanx of the patient, the proximal head having central core portionand a plurality of proximal wings extending radially outwardly from thecentral core portion.
 10. The intramedullary fixation device of claim 9,wherein the radially projecting distal wings are spaced asymmetricallyabout the central core portion.
 11. The intramedullary fixation deviceof claim 9, wherein the distal head has a first maximum width and theproximal head has a second maximum width, the first maximum width beinggreater than the second maximum width.
 12. The intramedullary fixationdevice of claim 9, wherein the distal head has a first longitudinal winglength and the proximal head has a second longitudinal wing length, thefirst longitudinal wing length being less than the second longitudinalwing length.
 13. The intramedullary fixation device of claim 9, whereinthe asymmetrically spaced, radially projecting distal wings form aT-shape.
 14. The intramedullary fixation device of claim 9, furthercomprising a planar surface extending entirely across the transversewidth of the distal head portion.
 15. The intramedullary fixation deviceof claim 9, wherein at least one the proximal wings or the distal wingsis wedge-shaped.
 16. The intramedullary fixation device of claim 9,wherein each proximal wing comprises an outer surface portion forming anouter perimeter surface, the outer surface portion comprising an outerperimeter surface portion and a curved leading surface portion, thecurved leading surface portion curving from the outer perimeter surfaceportion and smoothly intersecting at the central core portion of theproximal head, each proximal wing also comprising a distally facingtrailing surface portion substantially perpendicular to the longitudinalaxis of the rigid body.
 17. The intramedullary fixation device of claim16, wherein each distal wing comprising an outer surface portion havingan outer perimeter surface portion and a curved leading surface portion,the curved leading surface portion curving from the outer perimetersurface portion and smoothly intersecting at the central core portion ofthe distal head, each wing of the distal head also comprising aproximally facing trailing surface portion substantially perpendicularto the longitudinal axis of the rigid body.